Steel in aircraft construction, 1935-45?

[MiTasol]

One of the many well known causes of corrosion in aircraft is dissimilar metal corrosion.

On the Hurricane, and many of the Hawker biplanes,

• the longerons were high strength steel,
• the diagonals were a mix of high strength steel and aluminium alloy,
• the machined parts were mainly steel,
• some of the horizontal spreaders were steel tubes with aluminium alloy ball fittings shrunk in to the ends,
• the plates that held the joints together were usually stainless steel,
• the bolts and rivets that held the whole lot together were steel.
• I seem to remember that the spacers that prevented the tubes from crushing when the bolts and rivets were tightened were aluminium alloy as well

The wing CC had steel spars, spreaders and diagonals with alloy ribs and skins. The early wing panels had steel spars with steel diagonals and alloy formers and skins. There were multiple types of later wings and AFAIK they all had alloy spars, pressed alloy ribs and alloy skins.

 

[tomo pauk]

On the Hurricane, and many of the Hawker biplanes,

• the longerons were high strength steel,
• the diagonals were high a mix of high strength steel and aluminium alloy,
• the horizontal spreaders were steel tubes with aluminium alloy ball fittings shrunk in to the ends,
• the plates that held the joints together were usually stainless steel,
• the bolts and rivets that held the whole lot together were steel.

Was the corrosion a problem on these aircraft, while these aircraft were in service?

 

[MiTasol]

Probably not because they basically had a very short expected service life. New designs came out every couple of years - unlike today when many of the in-service aircraft have been around for fifty odd years and B-52 aircraft built from 1952 to 1962 are still in service well over sixty years later.

None the less most of the US aircraft of the period were built of alclad when lighter unclad alloy would have sufficed.

 

[tomo pauk]

None the less most of the US aircraft of the period were built of alclad when lighter unclad alloy would have sufficed.

That is very interesting. What was the weight difference?

 

[swampyankee]

Can any you engineering types out there name a hypereutectic alloy suitable for engine blocks?

A319 or A356, per Aluminum-Silicon (Al-Si) Alloys: Properties, Applications, and Benefits – tensemetal

 

[MiTasol]

That is very interesting. What was the weight difference?

It varies by material thickness. At that time the cladding was typically .004 so on .025 material you are looking at about 16% of the thickness of the material whereas on .125 material you are looking at only about 3% of the material thickness. The cladding has a different SG to the alloy itself and each alloy has its own SG but the percentage of thickness is a rough guide. Most of the light structure and skins were between .025 and .050 so overall it added a significant load.

Reportedly, part of the weight reduction on the P-40N was from changing to unclad alloy sheet but I have never seen how much that saved.

 

[Shortround6]

Reportedly, part of the weight reduction on the P-40N was from changing to unclad alloy sheet but I have never seen how much that saved.

Apparently not much as in the weight breakdowns in AHT there is only about 160-180lbs difference in empty weight from the P-40K/M and a late P-40N. And since approximately 60lbs of that was the difference in the landing gear(aluminum wheels?) and there is only a few pounds of difference in the weight of the wing, fuselage and tail (normal manufacturing tolerance?) perhaps the report is in error or the change was more for cost/supply rather than for weight.

 

[MiTasol]

you are probably correct.
All P-40's had Hayes alloy wheels but the N had 27" wheels and all earlier ones had 30". The hole in the wing where they fit is the same tho. There were four different 27" wheels as the first three part numbers were prone to cracking.

 

[fshort]

Hi all:

I was shocked back in the '90's when I went into Herb Tischler's hangar at Meacham Field to see the progress on the 8-262 replicas he was building - the 1-piece main spar was steel! I knew about the fwd nose skins being sheet steel, but not the spars.

He had built really fabulous tooling - assembly jigs & was building parts for 5 airplanes.

I worked at a LearJet shop at the time & his guys came to ask us about CJ-610 engines.

He sure built alot of airplanes: a P-6E, F3Fs, Me 262s, Ki-43s - the Oscars were really impressive to me, as I saw a 10 x 10 crate full of corroded parts at Doug Champlin's shop. They told me that was an "Oscar in a box".

I heard that he was an apprentice at one of the German aircraft factories during WWII, and the parts he built were better than the production parts - but the Germans threw them away
because he was an apprentice!

Regards,
James